Medical Illustrations

Finger Anatomy: Fingers are easily injured, and broken fingers are some of the most common traumatic injuries seen in an emergency room. Finger fractures may account for up to 10% of all bone fractures. Because fingers are used for many everyday activities, they are at higher risk than other parts of the body for traumatic injury, including sports injuries, workplace injuries, and other accidents.

Understanding the basic anatomy of the hand and fingers is useful in understanding different types of finger injuries, broken fingers, and how some treatments differ from others. Fingers are constructed of ligaments (strong supportive tissue connecting bone to bone), tendons (attachment tissue from muscle to bone), and three  phalanges (bones). There are no muscles in the fingers; and fingers move by the pull of forearm muscles on the tendons. The three bones in each finger are named according to their relationship to the palm of the hand. The first bone, closest to the palm, is the proximal phalange; the second bone is the middle phalange; and the smallest and farthest from the hand is the distal phalange. The thumb does not have a middle phalange.

The knuckles are joints formed by the bones of the fingers and are commonly injured or dislocated with trauma to the hand.

• The first and largest knuckle is the junction between the hand and the fingers - the metacarpophalangeal joint (MCP). This joint commonly is injured in closed-fist activities and is commonly known as a boxer's fracture.
  
  
• The next knuckle out toward the fingernail is the proximal inter-phalangeal joint (PIP). This joint may be dislocated in sporting events when a ball or object directly strikes the finger.
  
  
• The farthest joint of the finger is the distal inter-phalangeal joint (DIP). Injuries to this joint usually involve a fracture or torn tendon (avulsion) injury.